北京“7·21”特大暴雨诱发的地质灾害类型及其特征分析

Types and characteristics of geological disasters induced by the “7·21” rainstorm in Beijing

降雨是突发地质灾害主要诱因之一,文章通过剖析降雨及其引发的地质灾害的典型案例,研究突发地质灾害时空分布特点及规律,为极端气象条件下的防灾减灾提供技术支持。文中对北京市有气象记录以来强度最大的“7·21”特大暴雨及其引发的地质灾害数据进行系统分析,分析不同类型的突发地质灾害数量、规模、灾情与降雨量及降雨强度之间的响应关系,重点研究了北京西部山区短时强降雨泥石流发生的阈值。结果显示,随着与降雨中心距离的增加,突发地质灾害的数量、种类及规模逐渐变少,降雨强度是诱发突发地质灾害的关键因素;不同类型突发地质灾害的激发雨量和雨强具有明显差别,泥石流、滑坡的触发雨量与雨强高于崩塌;北京山区诱发泥石流的累计降雨量阈值为187.4~257.2 mm,小时雨强阈值为51.2~62 mm。基于研究结果将“7·21”触发泥石流的实时数据与以往基于平均雨强的泥石流临界雨量进行对比,对北京基于平均雨强的临界雨量模型进行了修正,为提高地质灾害的预警预报精度提供技术保障。

Because of rainfall is one of the main inducing factors of sudden geological disasters,by analyzing the temporal and spatial distribution characteristics of typical rainfall and the induced geological disasters,this paper studies the characteristics and laws of different types of rainfall and its induced sudden geological disasters,so as to provide technical support for disaster prevention and reduction under extreme meteorological conditions.Using the method of typical case analysis,this paper systematically analyzes the "7·21" rainstorm with the greatest intensity since the meteorological records in Beijing and its geological disaster data,and studies the response relationship between the number,scale and disaster situation of different types of sudden geological disasters and rainfall and rainfall intensity,This paper focuses on the threshold of short-term heavy rainfall debris flow in the mountainous area of western Beijing.The results show that with the increase of the distance from the rainfall center,the number,type and scale of sudden geological disasters gradually decrease,and the rainfall intensity is the key factor inducing the occurrence of sudden geological disasters.The triggered rainfall and rainfall intensity of different types of sudden geological disasters are obviously different.The triggered rainfall intensity and rainfall of debris flow and landslide are higher than that of collapse.The cumulative rainfall threshold of debris flow induced in Beijing mountainous area is 187.4-257.2 mm,and the hourly rainfall intensity threshold is 51.2-62 mm.Based on the research results,the real-time data of debris flow triggered by “7·21” are compared with the previous critical rainfall of debris flow based on average rainfall intensity,and the critical rainfall prediction model based on average rainfall intensity in Beijing is modified,so as to provide technical guarantee for improving the accuracy of early warning and prediction of geological disasters.